This invention relates to the field of heat exchangers, and more particularly to a shell and tube heat exchanger with plastic components.
Shell and tube heat exchangers are commonly used with marine engines for cooling. For use in seawater, they isolate the engine cooling system from the corrosive effects of the salt water. They are also found on stationary auxiliary generators, and in industrial and chemical process plants. Engine cooling systems typically use a mixture of ethylene glycol and de-ionized water as coolant. Ambient cooling water may be salty or fresh. Shell and tube heat exchangers are well known, and have taken a variety of configurations in the past. Some examples of heat exchangers in the prior art are shown in the following patents:
Schroeder, U.S. Pat. No. 5,746,270, discloses a metal body 54 with an outer wall 56. The ends of the outer wall 56 project inward to form a flange. This prevents removal of the tube bundle 60. It also precludes preassembly of the tube bundle as a module. The metal tubes are inserted into the body 54, and then welded together at their ends, the weld 61 forming a tube header.
McMorries, IV, U.S. Pat. No. 5,004,042, illustrates a tube bundle 46 with metal tubes 48 mounted in a plastic tube base (header) 58. Plastic end caps 94 and 96 are sealed against the header 58 by first O-rings 146, and against the shell 92 by second O-rings 148. Separator plates 86 to direct flow are integral with the end caps 92 and 96.
Helin, U.S. Pat. No. 3,187,810, shows tubes 21 mounted in a fixed header and a slideable header 19 to allow for expansion. Header 19 is sealed against shell flange 11 and head flange 15 by sealing rings 29 and 31, and packing 39 and 41, set into recess 37.
Myers, U.S. Pat. No. 3,572,429, discloses a shell 8 comprised of hubs 12 and14 welded to tubular member 10. Tubes 24 are mounted in fixed header 26 and slideable header 28 to allow for expansion. The tube/header bundle is removable from the shell 8. Two O-rings 42 and 44 are set into grooves in each hub 12 and 14 to seal the slideable header 28 to the shell 8. Inspection hole 72 between the O-rings 42 and 44 allows leak detection. Construction is all metal.
In all of the above devices, the inlet and outlet nozzles for both coolant and seawater are either welded to the shell and end caps, or are integrally cast. In no case is there provision for easy alignment and mounting of the nozzles. Nor can the location of the nozzles be changed without expensive tooling changes. In the prior-art devices, the separators are cast or welded integrally with the end caps or with the shell. In no prior-art invention can the separators be easily exchanged for new separators having either more or fewer dividers for more or fewer passes through the tube bundle, respectively. In the above-described devices, no means is shown for sealing the separator dividers against leakage at both the end caps and the headers. No means is provided for sealing the separator dividers against leakage during thermal expansion. None of the prior-art inventions have provision for grounding a metal tube bundle to the engine.
Accordingly, there is a need to provide a shell and tube heat exchanger that has inlet and outlet nozzles that can be located in various positions, and can be easily aligned and mounted.
There is a further need to provide a heat exchanger of the type described, in which the tube bundle, nozzles, end covers, and separators will be removable for cleaning or replacement.
There is yet a further need to provide a heat exchanger of the type described and that will provide separators of various divider plate configurations that are easy to install and service.
There is a still further need to provide a heat exchanger of the type described and that will provide for sealing the separator plates against leakage at both the end caps and the headers, even in the event of thermal expansion.
There is another need to provide a heat exchanger of the type described and that will provide for grounding and metal tube bundle to the engine.
This is yet another need to provide a heat exchanger of the type described and that will provide high thermal efficiency
There is still another need to provide a heat exchanger of the type described and that can be manufactured cost-effectively in large quantities of high quality.